It appears that people here
http://www.rojakpot.com/default.aspx...ar1=105&var2=0
have successfully flashed a Radeon 9800 Pro 128MB to a FireGL X2-128 using a hacked BIOS (there is no real FireGL X2 with 128MB memory, only 256, but the core is identical)
Seems like a reasonably good way to get a $600+ card for $200 if you are willing to play with BIOS flashing, the only thing you don't get is Dual DVI (the 9800 pro has one DVI and one VGA)